Communication devices for generating and using a matrix-mapped sequence

ABSTRACT

A communication device for generating a matrix-mapped sequence is described. The communication device includes sequence generation circuitry. The communication device also includes mapping circuitry coupled to the sequence generation circuitry. The mapping circuitry applies a first matrix with at least one column multiplied by −1 to a sequence. The communication device also includes a transmit block coupled to the mapping circuitry.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application for patent is a continuation of U.S. patentapplication Ser. No. 13/149,432, entitled “COMMUNICATION DEVICES FORGENERATING AND USING A MATRIX-MAPPED SEQUENCE,” filed May 31, 2011,pending, and U.S. Provisional Application No. 61/352,258, entitled“MAPPING MATRIX FOR 802.11AC VHT-LTF SYMBOLS,” filed Jun. 7, 2010, andassigned to the assignee hereof and hereby expressly incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to communication systems. Morespecifically, the present disclosure relates to communication devicesfor generating and using a matrix-mapped sequence.

BACKGROUND

Communication systems are widely deployed to provide various types ofcommunication content such as data, voice, video and so on. Thesesystems may be multiple-access systems capable of supportingsimultaneous communication of multiple communication devices (e.g.,wireless communication devices, access terminals, etc.) with one or moreother communication devices (e.g., base stations, access points, etc.).

Use of communication devices has dramatically increased over the pastfew years. Communication devices often provide access to a network, suchas a Local Area Network (LAN) or the Internet, for example. Othercommunication devices (e.g., access terminals, laptop computers, smartphones, media players, gaming devices, etc.) may wirelessly communicatewith communication devices that provide network access. Somecommunication devices comply with certain industry standards, such asthe Institute of Electrical and Electronics Engineers (IEEE) 802.11(e.g., Wireless Fidelity or “Wi-Fi”) standards. Communication deviceusers, for example, often connect to wireless networks using suchcommunication devices.

As the use of communication devices has increased, advancements incommunication device capacity, reliability and efficiency are beingsought. Systems and methods that improve communication device capacity,reliability and/or efficiency may be beneficial.

SUMMARY

A communication device for generating a matrix-mapped sequence isdisclosed. The communication device includes sequence generationcircuitry. The communication device also includes mapping circuitrycoupled to the sequence generation circuitry. The mapping circuitryapplies a first matrix with at least one column multiplied by −1 to asequence. The communication device additionally includes a transmitblock coupled to the mapping circuitry. The sequence may be a Very HighThroughput Long Training Field (VHT-LTF) sequence. The communicationdevice may be an access point. The communication device may be astation.

The first matrix may be a discrete Fourier transform (DFT) matrix. Thefirst matrix may be given according to an equation

$P_{6 \times 6} = {\begin{bmatrix}1 & {- 1} & 1 & 1 & 1 & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & w^{4} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & w^{8} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & w^{12} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & w^{16} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & w^{20} & {- w^{25}}\end{bmatrix}.}$

P_(6×6) may be the first matrix and w may be equal to

${\exp\left( \frac{- {j2\pi}}{6} \right)}.$

The first matrix may be applied to six sequences on five or six streams.

The mapping circuitry may apply a second matrix to a pilot sequence. Thesecond matrix may include a number of replicas of a first row of thefirst matrix.

A communication device for using a matrix-mapped sequence is alsodisclosed. The communication device may include a receive block. Thereceive block receives a sequence that is mapped according to a firstmatrix with at least one column multiplied by −1. The communicationdevice also includes channel estimation circuitry coupled to the receiveblock. The sequence may be a Very High Throughput Long Training Field(VHT-LTF) sequence. The channel estimation circuitry may estimate achannel based on the sequence. The communication device may be an accesspoint. The communication device may be a station.

The first matrix may be a discrete Fourier transform (DFT) matrix. Thefirst matrix may be given according to an equation

$P_{6 \times 6} = {\begin{bmatrix}1 & {- 1} & 1 & 1 & 1 & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & w^{4} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & w^{8} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & w^{12} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & w^{16} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & w^{20} & {- w^{25}}\end{bmatrix}.}$

P_(6×6) may be the first matrix and w may be equal to

${\exp\left( \frac{- {j2\pi}}{6} \right)}.$

The receive block may receive six sequences that are mapped according tothe first matrix with at least one column multiplied by −1.

The receive block may receive a pilot sequence that is mapped accordingto a second matrix. The second matrix may include a number of replicasof a first row of the first matrix.

The communication device may also include transmitter circuitry coupledto the channel estimation circuitry. The transmitter circuitry maytransmit a channel estimate based on the sequence.

A method for generating a matrix-mapped sequence on a communicationdevice is also disclosed. The method includes generating a sequence. Themethod also includes applying a first matrix with at least one columnmultiplied by −1 to the sequence. The method further includestransmitting the sequence.

A method for using a matrix-mapped sequence on a communication device isalso disclosed. The method includes receiving a sequence that is mappedaccording to a first matrix with at least one column multiplied by −1.The method also includes estimating a channel.

A computer-program product for generating a matrix-mapped sequence isalso disclosed. The computer-program product includes a non-transitorytangible computer-readable medium with instructions. The instructionsinclude code for causing a communication device to generate a sequence.The instructions also include code for causing the communication deviceto apply a first matrix with at least one column multiplied by −1 to thesequence. The instructions further include code for causing thecommunication device to transmit the sequence.

A computer-program product for using a matrix-mapped sequence is alsodisclosed. The computer-program product includes a non-transitorytangible computer-readable medium with instructions. The instructionsinclude code for causing a communication device to receive a sequencethat is mapped according to a first matrix with at least one columnmultiplied by −1. The instructions also include code for causing thecommunication device to estimate a channel.

An apparatus for generating a matrix-mapped sequence is also disclosed.The apparatus includes means for generating a sequence. The apparatusalso includes means for applying a first matrix with at least one columnmultiplied by −1 to the sequence. The apparatus additionally includesmeans for transmitting the sequence.

An apparatus for using a matrix-mapped sequence is also disclosed. Theapparatus includes means for receiving a sequence that is mappedaccording to a first matrix with at least one column multiplied by −1.The apparatus also includes means for estimating a channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating one configuration of atransmitting communication device and a receiving communication devicein which systems and methods for generating and using a matrix-mappedsequence may be implemented;

FIG. 2 is a diagram illustrating one example of a communication framethat may be used in accordance with the systems and methods disclosedherein;

FIG. 3 is a diagram illustrating a more specific example of acommunication frame that may be used in accordance with the systems andmethods disclosed herein;

FIG. 4 is a flow diagram illustrating one configuration of a method forgenerating a matrix-mapped sequence;

FIG. 5 is a flow diagram illustrating a more specific configuration of amethod for generating a matrix-mapped sequence;

FIG. 6 is a flow diagram illustrating another configuration of a methodfor using a matrix-mapped sequence;

FIG. 7 is a block diagram illustrating one configuration of an accesspoint (AP) and a station (STA) in which systems and methods for using amatrix-mapped sequence may be implemented;

FIG. 8 is a block diagram of a communication device that may be used ina multiple-input and multiple-output (MIMO) system;

FIG. 9 illustrates certain components that may be included within acommunication device; and

FIG. 10 illustrates certain components that may be included within awireless communication device.

DETAILED DESCRIPTION

Examples of communication devices include cellular telephone basestations or nodes, access points (APs), wireless gateways and wirelessrouters. A communication device may operate in accordance with certainindustry standards, such as the Institute of Electrical and ElectronicsEngineers (IEEE) 802.11a, 802.11b, 802.11g, 802.11n and/or 802.11ac(e.g., Wireless Fidelity or “Wi-Fi”) standards. Other examples ofstandards that a communication device may comply with include IEEE802.16 (e.g., Worldwide Interoperability for Microwave Access or“WiMAX”), Third Generation Partnership Project (3GPP), 3GPP Long TermEvolution (LTE) and others (e.g., where a communication device may bereferred to as a Node B, evolved Node B (eNB), etc.). While some of thesystems and methods disclosed herein may be described in terms of one ormore standards, this should not limit the scope of the disclosure, asthe systems and methods may be applicable to many systems and/orstandards.

Some communication devices (e.g., stations (STAs), access terminals,client devices, client stations, etc.) may wirelessly communicate withother communication devices. Some communication devices may be referredto as stations (STAs), mobile devices, mobile stations, subscriberstations, user equipments (UEs), remote stations, access terminals,mobile terminals, terminals, user terminals, subscriber units, etc.Additional examples of communication devices include laptop or desktopcomputers, cellular phones, smart phones, wireless modems, e-readers,tablet devices, gaming systems, etc. Some of these communication devicesmay operate in accordance with one or more industry standards asdescribed above. Thus, the general term “communication device” mayinclude communication devices described with varying nomenclaturesaccording to industry standards (e.g., station (STA), access terminal,user equipment (UE), remote terminal, access point (AP), base station,Node B, evolved Node B (eNB), etc.).

Some communication devices may be capable of providing access to acommunications network. Examples of communications networks include, butare not limited to, a telephone network (e.g., a “land-line” networksuch as the Public-Switched Telephone Network (PSTN) or cellular phonenetwork), the Internet, a Local Area Network (LAN), a Wide Area Network(WAN), a Metropolitan Area Network (MAN), etc.

It should be noted that the terms “couple,” “coupling,” “coupled” orother variations of the word couple as used herein may indicate eitheran indirect connection or a direct connection. For example, if a firstcomponent is “coupled” to a second component, the first component may beeither indirectly connected (e.g., through another component) to thesecond component or directly connected to the second component.Additionally, it should be noted that as used herein, designating acomponent, element or entity as a “first,” “second,” “third” or “fourth”component may be arbitrary and is used to distinguish components,elements or entities for explanatory clarity. It should also be notedthat labels used to designate a “second,” “third” or “fourth,” etc. donot necessarily imply that elements using preceding labels “first,”“second” or “third,” etc. are included or used. For example, simplybecause an element or component is labeled a “third” component does notnecessarily imply that “first” and “second” elements or components existor are used. In other words, the numerical labels (e.g., first, second,third, fourth, etc.) are labels used for ease in explanation and do notnecessarily imply a particular number of elements, a particular order ora particular structure. Thus, entities may be labeled or numbered in anymanner.

The IEEE 802.11 group's current work involves standardizing a new andfaster version of 802.11, under the name VHT (Very High Throughput).This extension may be referred to as 802.11ac. The use of additionalsignal bandwidth (BW) is also being considered such as transmissionsusing 80 megahertz (MHz) and 160 MHz. Physical-layer (PHY) preambles maybe used that allow for both increased signal bandwidth and that allowbackward compatibility to 802.11n, 802.11a, and 802.11.

An 802.11ac frame with a preamble may be structured including severalfields. In one configuration, an 802.11ac frame may include a legacyshort training field or non-high throughput short training field(L-STF), a legacy long training field or non-high throughput longtraining field (L-LTF), a legacy signal field or non-high throughputsignal field (L-SIG), one or more very high throughput signal fields A(VHT-SIG-A), a very high throughput short training field (VHT-STF), oneor more very high throughput long training fields (VHT-LTFs), a veryhigh throughput signal field B (VHT-SIG-B) and a data field (e.g., DATAor VHT-DATA). In some configurations, multiple VHT-SIG-As may be used(e.g., a VHT-SIG-A1 and a VHT-SIG-A2).

The systems and methods disclosed herein describe communication devicesfor generating and using a matrix-mapped sequence. In someconfigurations, the systems and methods disclosed herein may be appliedto IEEE 802.11 specifications. In an IEEE meeting, a six-by-six (e.g.,6×6) discrete Fourier transform (DFT) matrix was adopted as a matrix P(or “P matrix,” for example) for five or six space-time streams (intotal). Furthermore, a motion was adopted for using a matrix R (or “Rmatrix,” for example) for pilot mapping in a very high throughput longtraining field (VHT-LTF), where R comprises N_(STS) replicas of thefirst row of P and N_(STS) is a number of space-time streams.

One reason for choosing this R matrix was to avoid spectral lines on thepilots, which would happen if R is all ones. However, R is all ones forthe case of six VHT-LTFs, since the first row of the six-by-six P matrix(e.g., DFT matrix) consists of ones only when the systems and methodsdisclosed herein are not used. However, the systems and methodsdisclosed herein may resolve this problem by multiplying one or morecolumns of the P matrix (e.g., DFT matrix) by −1.

In one configuration, for instance, two columns of a six-by-six P matrixmay be multiplied by −1. One example of a modified six-by-six P matrixis illustrated in Equation (1).

$\begin{matrix}{P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & 1 & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & w^{4} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & w^{8} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & w^{12} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & w^{16} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & w^{20} & {- w^{25}}\end{bmatrix}} & (1)\end{matrix}$

In Equation (1), P_(6×6) is the P matrix and

$w = {{\exp\left( \frac{- {j2\pi}}{6} \right)}.}$

It may be observed that the first row of P_(6×6) in Equation (1) may beequal to the first row of a four-by-four P matrix {1,−1,1,1}, with thefirst two values repeated at the end. It should be noted thatmultiplying any column by −1 does not change the orthogonality of the Pmatrix.

Other alternative P matrices may be used in accordance with the systemsand methods disclosed herein. However, the modified P matrix illustratedin Equation (1) may be a logical choice as it reuses an existingfour-by-four (e.g., 4×4) P matrix that may also be used for aneight-by-eight (8×8) P matrix. Nevertheless, many alternatives may beused depending on the configuration. Other alternatives may be made bymultiplying any column or number of columns of an original six-by-six(e.g., 6×6) P matrix by −1. One example of an alternative is illustratedin Equation (2).

$\begin{matrix}{P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & {- w^{4}} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & {- w^{8}} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & {- w^{12}} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & {- w^{16}} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & {- w^{20}} & {- w^{25}}\end{bmatrix}} & (2)\end{matrix}$

In Equation (2), P_(6×6) is another example of a P matrix and

$w = {{\exp\left( \frac{- {j2\pi}}{6} \right)}.}$

In this example, the first row is equal to a first row of four-by-four(e.g., 4×4) P matrix {1,−1,1,1} with two −1 values added. This exampleprovides a zero direct current (DC) component in the first row thatminimizes the spectral line.

Various configurations are now described with reference to the Figures,where like reference numbers may indicate functionally similar elements.The systems and methods as generally described and illustrated in theFigures herein could be arranged and designed in a wide variety ofdifferent configurations. Thus, the following more detailed descriptionof several configurations, as represented in the Figures, is notintended to limit scope, as claimed, but is merely representative of thesystems and methods.

FIG. 1 is a block diagram illustrating one configuration of atransmitting communication device 102 and a receiving communicationdevice 134 in which systems and methods for generating and using amatrix-mapped sequence may be implemented. Examples of the transmittingcommunication device 102 may include access points, access terminals,base stations, user equipments (UEs), stations (STAs), etc. Examples ofthe receiving communication device 134 may include access points, accessterminals, base stations, user equipments (UEs), stations (STAs), etc.The transmitting communication device 102 may include a sequencegeneration block/module 104, a pilot insertion block/module 106, amapping block/module 108, a cyclic shift block/module 114, a spatialmapping block/module 116, an Inverse Discrete Fourier Transform (IDFT)block/module 118, a guard interval block/module 120, one or moretransmit radio frequency blocks 122, one or more antennas 128 a-n, apseudo-random noise generator 124 and/or a pilot generator 126.

It should be noted that one or more of the elements 104, 106, 108, 114,116, 118, 120, 122, 124, 126 included in the transmitting communicationdevice 102 may be implemented in hardware, software or a combination ofboth. For instance, one or more of the elements 104, 106, 108, 114, 116,118, 120, 122, 124, 126 included in the transmitting communicationdevice 102 may be implemented as circuitry (e.g., integrated circuits,application specific integrated circuits (ASICs), a processor, etc.)and/or using a processor and instructions. For instance, the systems andmethods disclosed herein may be implemented using a processor and/or maybe hard-coded in a register transfer level (RTL) in a communicationdevice (e.g., transmitting communication device 102, receivingcommunication device 134, etc.). Furthermore, the term “block/module”may be used to indicate that a particular element may be implemented inhardware, software or a combination of both.

It should also be noted that although some of the elements 104, 106,108, 114, 116, 118, 120, 122, 124, 126 may be illustrated as a singleblock, one or more of the elements 104, 106, 108, 114, 116, 118, 120,122, 124, 126 illustrated may comprise multiple parallel blocks/modulesin some configurations. For instance, multiple sequence generationblocks/modules 104, multiple pilot insertion blocks/modules 106,multiple mapping blocks/modules 108, multiple cyclic shiftblocks/modules 114, multiple spatial mapping blocks/modules 116,multiple inverse discrete Fourier transform blocks/modules 118, multipleguard interval blocks/modules 120 and/or multiple transmit radiofrequency blocks 122 may be used to form multiple paths in someconfigurations.

For instance, separate streams 130 (e.g., space-time streams 130,spatial streams 130, etc.) may be generated and/or transmitted usingseparate paths. In some implementations, these paths are implementedwith distinct hardware, whereas in other implementations, the pathhardware is reused for more than one stream 130 or the path logic isimplemented in software that executes for one or more streams 130. Morespecifically, each of the elements illustrated in the transmittingcommunication device 102 may be implemented as a single block/module oras multiple blocks/modules.

The sequence generation block/module 104 may generate one or moresequences (e.g., training sequences, “VHT-LTF data,” “VHT-LTFsequences,” etc.). For example, the sequence generation block/module 104may generate one or more training sequences for each VHT-LTF to betransmitted in a frame. In some configurations, the sequence generationblock/module 104 may generate a sequence in the frequency domain basedon an amount of transmission bandwidth. For example, different sequencesmay be generated based on whether 20 megahertz (MHz), 40 MHz, 80 MHz or160 MHz of bandwidth is allocated for transmission. The sequence(s) maybe provided to the pilot insertion block/module 106.

The pilot generator 126 may generate a pilot sequence. A pilot sequencemay be a group of pilot symbols. In one configuration, for instance, thevalues in the pilot sequence may be represented by a signal with aparticular phase, amplitude and/or frequency. For example, a “1” maydenote a pilot symbol with a particular phase and/or amplitude, while a“−1” may denote a pilot symbol with a different (e.g., opposite orinverse) phase and/or amplitude.

The transmitting communication device 102 may include a pseudo-randomnoise generator 124 in some configurations. The pseudo-random noisegenerator 124 may generate a pseudo-random noise sequence or signal(e.g., values) used to scramble the pilot sequence. For example, thepilot sequence for successive orthogonal frequency-division multiplexing(OFDM) symbols may be multiplied by successive numbers from thepseudo-random noise sequence, thereby scrambling the pilot sequence perOFDM symbol.

The pilot insertion block/module 106 inserts pilot tones into pilot tonesubcarriers 132. For example, the pilot sequence may be mapped tosubcarriers 132 at particular indices. For instance, pilot symbols fromthe (scrambled) pilot sequence may be mapped to pilot subcarriers 132that are interspersed with data subcarriers 132 and/or other subcarriers132. In other words, the pilot sequence or signal may be combined withthe data sequence or signal. In some configurations, one or more directcurrent (DC) tones may be centered at a subcarrier index 0. The pilotinsertion block/module 106 may apply phase rotation to the combinedsignal (e.g., to one or more 20 MHz subbands) in some configurations.

The combined data and pilot signal may be provided to the mappingblock/module 108. The mapping block/module 108 may apply matrix mappingto the data tones (e.g., a training sequence) and/or to the pilot tones(e.g., pilot sequence) included in the combined signal to produce amatrix-mapped signal. The mapping block/module 108 may include a firstmatrix 110 and/or a second matrix 112. For convenience, the first matrix110 is illustrated as and may be referred to as a P matrix 110.Furthermore, the second matrix 112 is illustrated as and may be referredto as an R matrix 112. However, it should be noted that the first matrix110 and the second matrix 112 may be referred to differently in otherconfigurations. It should be noted that the functionality of the mappingblock/module 108, the P matrix 110 and/or the R matrix 112 may beimplemented using a processor and/or hard-coded in an RTL on thetransmitting communication device 102 in some configurations.

In one example, the first matrix 110 (e.g., P matrix 110) provides amapping for the data tones (e.g., sequence, training sequence, etc.) inone or more very high throughput long training fields (VHT-LTFs). Thefirst matrix 110 (e.g., P matrix 110) may have at least one of its 110columns multiplied by −1. For example, the first matrix 110 may be a DFTmatrix P_(original) that has had one or more of its columns multipliedby −1, where P_(original) is given in Equation (3).

$\begin{matrix}{P_{original} = \begin{bmatrix}1 & 1 & 1 & 1 & 1 & 1 \\1 & w^{1} & w^{2} & w^{3} & w^{4} & w^{5} \\1 & w^{2} & w^{4} & w^{6} & w^{8} & w^{10} \\1 & w^{3} & w^{6} & w^{9} & w^{12} & w^{15} \\1 & w^{4} & w^{8} & w^{12} & w^{16} & w^{20} \\1 & w^{5} & w^{10} & w^{15} & w^{20} & w^{25}\end{bmatrix}} & (3)\end{matrix}$

In Equation (3),

$w = {{\exp \left( \frac{- {j2\pi}}{6} \right)}.}$

One specific example of the first matrix 110 (e.g., P matrix 110) is

$P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & 1 & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & w^{4} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & w^{8} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & w^{12} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & w^{16} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & w^{20} & {- w^{25}}\end{bmatrix}$

as given above in Equation (1). The example given in Equation (1) may beused because the first row of P_(6×6) in Equation (1) may be equal tothe first row of a four-by-four P matrix {1,−1,1,1}, with the first twovalues repeated at the end. It should be noted that multiplying anycolumn by −1 does not change the orthogonality of the P matrix 110.Another specific example of the first matrix 110 (e.g., P matrix 110) isgiven above in Equation (2).

The data tones (e.g., training sequence, VHT-LTF sequence) in thecombined signal may be multiplied by elements of the P matrix 110. Forexample, each column of the P matrix 110 may correspond to a VHT-LTF andeach row of the P matrix 110 may correspond to a stream 130. Thus, theexample of the P matrix 110 given in Equation (1) may be applied to sixsequences (e.g., six VHT-LTFs) on six streams 130 (e.g., spatial streams130 or space-time streams 130). More specifically, for instance, datatones in a first VHT-LTF on a first stream 130 may be multiplied by theelement in the first column and first row of the P matrix 110.Furthermore, data tones in a second VHT-LTF on a first stream may bemultiplied by the second element in the first row of the P matrix 110and so on. It should be noted that a six-by-six P matrix 110 may beapplied when five or six streams 130 (e.g., spatial streams 130,space-time streams 130) are used for transmitting data tones (e.g., oneor more training sequences) in some configurations. Other P matrices maybe used for different numbers of streams 130, for instance.

In one configuration, the second matrix 112 (e.g., R matrix 112)provides a mapping for the pilot tones in one or more VHT-LTFs. Forexample, the pilot tones in one or more VHT-LTFs on one or more streams130 (e.g., spatial streams 130 or space-time streams 130) may bemultiplied by the R matrix 112.

The second matrix 112 (e.g., R matrix 112) may include a number ofreplicas of the first row of the first matrix 110 (e.g., P matrix 110).In one configuration, the R matrix 112 includes N_(STS) replicas of thefirst row of the P matrix 110, where N_(STS) is a number of space-timestreams 130. As described above, one problem addressed by the systemsand methods disclosed herein is the formation of spectral lines on thepilots. This may occur if the first row of a P matrix is all ones in thecase of six VHT-LTFs. However, in accordance with the systems andmethods disclosed herein, one or more of the columns of the P matrix 110may be multiplied by −1, thus avoiding a first row of all ones in the Pmatrix 110.

The output of the mapping block/module 108 (e.g., a matrix-mappedsignal) may be provided to the cyclic shift block/module 114. The cyclicshift block/module 114 may insert cyclic shifts to one or more streams130 (e.g., spatial streams 130 or space-time streams 130) for cyclicshift diversity (CSD). In one configuration, cyclic shifts may beapplied to multiple transmit chains.

The output of the cyclic shift block/module 114 may be provided to aspatial mapping block/module 116. The spatial mapping block/module 116may map output of the cyclic shift block/module 114 (e.g., data tonesand/or pilot tones) to one or more streams 130 (e.g., spatial streams130 or space-time streams 130).

The IDFT block/module 118 may perform an inverse discrete Fouriertransform on the signal provided by the spatial mapping block/module116. For example, the inverse discrete Fourier transform (IDFT)block/module 118 converts the frequency signals of the data tones and/orpilot tones into time domain signals representing the signal over thestreams 130 and/or time-domain samples for a symbol period. In oneconfiguration, for example, the IDFT block/module 118 may perform aninverse fast Fourier transform (IFFT).

The signal output from the IDFT block/module 118 may be provided to theguard interval block/module 120. The guard interval block/module 120 mayinsert (e.g., prepend) a guard interval to the signal output from theIDFT block/module 118. For example, the guard interval block/module 120may insert an 800 nanosecond (ns) guard interval. In someconfigurations, the guard interval block/module 120 may additionallyperform windowing on the signal.

The output of the guard interval block/module 120 may be provided to thetransmit radio frequency block(s) 122. The transmit radio frequencyblock(s) 122 may upconvert the output of the guard interval block/module120 (e.g., a complex baseband waveform) and transmit the resultingsignal using the one or more antennas 128 a-n. For example, the one ormore transmit radio frequency block(s) 122 may output radio-frequency(RF) signals to one or more antennas 128 a-n, thereby transmitting thedata tones (e.g., VHT-LTF sequence) and/or pilot tones (e.g., VHT-LTFpilots) over a wireless medium suitably configured for receipt by one ormore receiving communication devices 134.

It should be noted that the transmitting communication device 102 maydetermine channel bandwidth to be used for transmissions to one or morereceiving communication devices 134. This determination may be based onone or more factors, such as receiving communication device 134compatibility, number of receiving communication devices 134 (to use thecommunication channel), channel quality (e.g., channel noise) and/or areceived indicator, etc. In one configuration, the transmittingcommunication device 102 may determine whether the bandwidth for signaltransmission is 20 MHz, 40 MHz, 80 MHz or 160 MHz.

One or more of the elements 104, 106, 108, 114, 116, 118, 120, 122, 124,126 included in the transmitting communication device 102 may operatebased on the bandwidth determination. For example, the sequencegeneration block/module 104 may generate one or more particular trainingsequences (e.g., VHT-LTF data tones) based on transmission bandwidth.Additionally or alternatively, the pilot generator 126 may generate anumber of pilot symbols based on the bandwidth for signal transmission.For example, the pilot generator 126 may generate a certain number ofpilot symbols for an 80 MHz signal. It should be noted that the tones orsubcarriers 132 may be orthogonal frequency-division multiplexing (OFDM)subcarriers 132 in some configurations.

Additionally, the pilot insertion block/module 106 may insert pilottones based on a bandwidth for signal transmission. For instance, thepilot insertion block/module 106 may insert pilot symbols into pilottones (e.g., pilot subcarriers 132) based on a bandwidth for signaltransmission.

Additionally, the mapping block/module 108 may matrix map the data tonesand/or pilot tones based on the bandwidth for signal transmission. Forinstance, the mapping block/module 108 may matrix map a number of datatones (e.g., data subcarriers 132) and a number of pilot tones (e.g.,pilot subcarriers 132) based on a bandwidth for signal transmission.

One or more streams 130 may be transmitted from the transmittingcommunication device 102 such that the transmissions on differentstreams 130 may be differentiable at a receiving communication device134 (with some probability). For example, bits mapped to one spatialdimension are transmitted as one stream 130. That stream 130 might betransmitted on its own antenna 128 spatially separate from otherantennas 128, its own orthogonal superposition over a plurality ofspatially-separated antennas 128, its own polarization, etc. Manytechniques for stream 130 separation (involving separating antennas 128in space or other techniques that would allow their signals to bedistinguished at a receiver, for example) are known and can be used. Inthe example shown in FIG. 1, there are one or more streams 130 that aretransmitted using the same or a different number of antennas 128 a-n(e.g., one or more).

In the case that the transmitting communication device 102 uses aplurality of frequency subcarriers 132, there are multiple values forthe frequency dimension, such that some data (e.g., some VHT-LTF data)may be mapped to one frequency subcarrier 132 and other data (e.g.,other VHT-LTF data) to another frequency subcarrier 132. Other frequencysubcarriers 132 may be reserved as guard bands, pilot tone subcarriers132, or the like that do not (or do not always) carry data. For example,there may be one or more data subcarriers 132 and one or more pilotsubcarriers 132. It should be noted that, in some instances orconfigurations, not all subcarriers 132 may be excited at once. Forinstance, some tones may not be excited to enable filtering. In oneconfiguration, the transmitting communication device 102 may utilizeorthogonal frequency-division multiplexing (OFDM) for the transmissionof multiple subcarriers 132.

The time dimension refers to symbol periods. Different bits may beallocated to different symbol periods. Where there are multiple streams130, multiple subcarriers 132 and multiple symbol periods, thetransmission for one symbol period might be referred to as an “OFDM(orthogonal frequency-division multiplexing) MIMO (multiple-input,multiple-output) symbol.” A transmission rate for encoded data may bedetermined by multiplying the number of bits per simple symbol (e.g.,log₂ of the number of constellations used) times the number of streams130 times the number of data subcarriers 132, divided by the length ofthe symbol period.

One or more receiving communication devices 134 may receive and usesignals from the transmitting communication device 102. For example, areceiving communication device 134 may use a received bandwidthindicator to receive a given number of OFDM tones or subcarriers 132. Inone configuration, a receiving communication device 134 may use aVHT-LTF sequence generated by and received from the transmittingcommunication device 102 to estimate the channel.

It should be noted that one or more of the elements 138, 140, 142, 144,146, 148, 150, 152 included in the receiving communication device 134may be implemented in hardware, software or a combination of both. Forinstance, one or more of the elements 138, 140, 142, 144, 146, 148, 150,152 included in the receiving communication device 134 may beimplemented as circuitry (e.g., integrated circuits, applicationspecific integrated circuits (ASICs), a processor, etc.) and/or using aprocessor and instructions. For instance, the systems and methodsdisclosed herein may be implemented using a processor and/or may behard-coded in a register transfer level (RTL) in a communication device(e.g., transmitting communication device 102, receiving communicationdevice 134, etc.). It should also be noted that although some of theelements 138, 140, 142, 144, 146, 148, 150, 152 may be illustrated as asingle block, one or more of the elements 138, 140, 142, 144, 146, 148,150, 152 illustrated may comprise multiple parallel blocks/modules insome configurations.

A receiving communication device 134 may include one or more antennas154 a-n (which may be greater than, less than or equal to the number oftransmitting communication device 102 antennas 128 a-n and/or the numberof streams 130) that feed to one or more receive radio frequency blocks152. The receive radio frequency block(s) 152 (e.g., receive block(s))may output analog signals to one or more analog-to-digital converters(ADCs) 150. For example, a receive radio-frequency block 152 may receiveand downconvert a signal, which may be provided to an analog-to-digitalconverter 150. As with the transmitting communication device 102, thenumber of streams 130 processed may or may not be equal to the number ofantennas 154 a-n. Furthermore, each stream 130 need not be limited toone antenna 154, as various beamsteering, orthogonalization, etc.techniques may be used to arrive at a plurality of receiver streams.

The one or more analog-to-digital converters (ADCs) 150 may convert thereceived analog signal(s) to one or more digital signal(s). Theoutput(s) of the one or more analog-to-digital converters (ADCs) 150 maybe provided to one or more time and/or frequency synchronizationblocks/modules 148. A time and/or frequency synchronization block/module148 may (attempt to) synchronize or align the digital signal in timeand/or frequency (to a receiving communication device 134 clock, forexample).

The (synchronized) output of the time and/or frequency synchronizationblock(s)/module(s) 148 may be provided to one or more deformatters 146.For example, a deformatter 146 may receive an output of the time and/orfrequency synchronization block(s)/module(s) 148, remove guardintervals, etc. and/or parallelize the data for discrete Fouriertransform (DFT) processing.

One or more deformatter 146 outputs may be provided to one or morediscrete Fourier transform (DFT) blocks/modules 144. The discreteFourier transform (DFT) blocks/modules 144 may convert one or moresignals from the time domain to the frequency domain. A pilot processor142 may use the frequency domain signals (per stream 130, for example)to determine one or more pilot tones (over the streams 130, frequencysubcarriers 132 and/or groups of symbol periods, for example) sent bythe transmitting communication device 102. The pilot processor 142 mayadditionally or alternatively de-scramble the pilot sequence. The pilotprocessor 142 may use one or more pilot sequences described herein forphase, frequency and/or amplitude tracking. The pilot tone(s) may beprovided to a space-time-frequency detection and/or decodingblock/module 140, which may detect and/or decode the data over thevarious dimensions. The space-time-frequency detection and/or decodingblock/module 140 may output received data 136 (e.g., the receivingcommunication device's 134 estimation of data transmitted by thetransmitting communication device 102).

In some configurations, the receiving communication device 134 knows thesequences (e.g., VHT-LTF data, training sequences, etc.) sent as part ofa total information sequence. The receiving communication device 134 mayperform channel estimation with the aid of these known sequences. Toassist with pilot tone tracking, processing and/or data detection anddecoding, a channel estimation block/module 138 (e.g., channelestimation circuitry 138) may provide estimation signals (e.g., channelestimates) to the pilot processor 142 and/or the space-time-frequencydetection and/or decoding block/module 140 based on the output from thetime and/or frequency synchronization block/module 148. Alternatively,if the de-formatting and discrete Fourier transform is the same for theknown transmit sequences as for the payload data portion of the totalinformation sequence, the estimation signals may be provided to thepilot processor 142 and/or the space-time-frequency detection and/ordecoding block/module 140 based on the output from the discrete Fouriertransform (DFT) blocks/modules 144.

In accordance with the systems and methods disclosed herein, thereceiving communication device 134 may receive a sequence (e.g., VHT-LTFdata) that is mapped according to a matrix with a least one columnmultiplied by −1. For example, the receiving communication device 134may receive a VHT-LTF sequence or VHT-LTF data (e.g., training sequence)that has been mapped using the P matrix 110 that has at least one of itscolumns multiplied by −1. For instance, the DFT matrix illustrated inEquation (3) with one or more of its columns multiplied by −1 may beused to map the VHT-LTF data or sequence that is received by thereceiving communication device 134.

The receiving communication device 134 (e.g., channel estimationblock/module 138) may use the received data or sequence to generate achannel estimate. The receiving communication device 134 may use thechannel estimate to improve communications between the transmittingcommunication device 102 and the receiving communication device 134. Forexample, the receiving communication device 134 may use the channelestimate to better receive (e.g., demodulate, decode, etc.) data sentfrom the transmitting communication device 102. Additionally oralternatively, the receiving communication device 134 may send thechannel estimate (as feedback) to the transmitting communication device102 for use in precoding, beamsteering, etc. In some configurations, forinstance, the receiving communication device 134 may include atransmitter or transmitter circuitry (not shown in FIG. 1) fortransmitting the channel estimate to the transmitting communicationdevice 102. Accordingly, the transmitting communication device 102 mayalso include a receiver (not shown in FIG. 1) for receiving signals(such as the channel estimate) from the receiving communication device134 in some configurations. Received pilot tones in the VHT-LTF may beused to track frequency and phase offset in received transmissions.

In some configurations, the receiving communication device 134 maydetermine a channel bandwidth (for received communications). Forexample, the receiving communication device 134 may receive a bandwidthindication from the transmitting communication device 102 that indicatesa channel bandwidth. For instance, the receiving communication device134 may obtain an explicit or implicit bandwidth indication. In oneconfiguration, the bandwidth indication may indicate a channel bandwidthof 20 MHz, 40 MHz, 80 MHz or 160 MHz. The receiving communication device134 may determine the bandwidth for received communications based onthis indication and provide an indication of the determined bandwidth tothe pilot processor 142 and/or to the space-time-frequencydetection/decoding block/module 140.

FIG. 2 is a diagram illustrating one example of a communication frame200 that may be used in accordance with the systems and methodsdisclosed herein. The frame 200 may include one or more sections orfields for preamble symbols, pilot symbols and/or data symbols. Forexample, the frame 200 may comprise an 802.11ac preamble 264 and a datafield 272 (e.g., DATA or VHT-DATA field). In one configuration, the802.11ac preamble 264 may have a duration of 40 to 68 microseconds (μs).The preamble 264 and/or pilot symbols may be used (by a receivingcommunication device 134, for example) to synchronize, detect,demodulate and/or decode data included in the frame 200.

The frame 200 with an 802.11ac preamble 264 may be structured includingseveral fields. In one configuration, an 802.11ac frame 200 may includea legacy short training field or non-high throughput short trainingfield (L-STF) 256, a legacy long training field or non-high throughputlong training field (L-LTF) 258, a legacy signal field or non-highthroughput signal field (L-SIG) 260, one or more very high throughputsignal symbols or fields A (VHT-SIG-A) 262 (e.g., VHT-SIG-A1,VHT-SIG-A2, etc.), a very high throughput short training field (VHT-STF)266, one or more very high throughput long training fields (VHT-LTFs)268, a very high throughput signal field B (VHT-SIG-B) 270 and a datafield (DATA) 272.

The 802.11ac preamble 264 may accommodate backwards compatibility (withearlier 802.11 specifications, for instance). The first part of thepreamble 264 may include the L-STF 256, L-LTF 258, L-SIG 260 andVHT-SIG-A 262. This first part of the preamble 264 may be decodable bylegacy devices (e.g., devices that comply with legacy or earlierspecifications).

A second part of the preamble 264 includes the VHT-STF 266, one or moreVHT-LTFs 268, and the VHT-SIG-B 270. The second part of the preamble 264may not be decodable by legacy devices (or even by all 802.11ac devices,for instance).

The 802.11ac preamble 264 may include some control data that isdecodable by legacy 802.11a and 802.11n receivers. This control data maybe contained in the L-SIG 260. The data in the L-SIG 260 informs allreceivers how long the transmission will occupy the wireless medium, sothat all devices may defer their transmissions for an accurate amount oftime. Additionally, the 802.11ac preamble 264 may allow 802.11ac devicesto distinguish the transmission as an 802.11ac transmission (and avoiddetermining that the transmission is in an 802.11a or 802.11n format,for example).

In accordance with the systems and methods disclosed herein, the one ormore VHT-LTFs 268 may be mapped using a first matrix (e.g., P matrix)110 with at least one column multiplied by −1. For example, when five orsix streams 130 are used for transmitting VHT-LTFs 268, then sixVHT-LTFs 268 may be used in the frame (e.g., packet) 200. A transmittingcommunication device 102 may apply the first matrix (e.g., P matrix) 110to a sequence (e.g., VHT-LTF data) included in each VHT-LTF 268. Forinstance, the first matrix (e.g., P matrix) 110 may be applied to sixsequences (e.g., VHT-LTFs 268) on five or six streams 130. Thetransmitting communication device 102 may additionally apply a secondmatrix (e.g., R matrix) 112 to pilots (e.g., a pilot sequence) includedin each VHT-LTF 268.

FIG. 3 is a diagram illustrating a more specific example of acommunication frame 300 that may be used in accordance with the systemsand methods disclosed herein. The frame 300 may include one or moresections or fields for preamble symbols, pilot symbols and/or datasymbols. For example, the frame 300 may comprise an 802.11ac preamble364 and a data field 372 (e.g., DATA or VHT-DATA field). In oneconfiguration, the 802.11ac preamble 364 may have a duration of 40 to 68μs. The preamble 364 and/or pilot symbols may be used (by a receivingcommunication device 134, for example) to synchronize, detect,demodulate and/or decode data included in the frame 300.

The frame 300 with an 802.11ac preamble 364 may be structured includingseveral fields. In one configuration, an 802.11ac frame 300 may includea legacy short training field or non-high throughput short trainingfield (L-STF) 356, a legacy long training field or non-high throughputlong training field (L-LTF) 358, a legacy signal field or non-highthroughput signal field (L-SIG) 360, a very high throughput signal fieldA1 (VHT-SIG-A1) 362 a, a VHT-SIG-A2 362 b, a very high throughput shorttraining field (VHT-STF) 366, six very high throughput long trainingfields (VHT-LTFs) 368 a-f, a very high throughput signal field B(VHT-SIG-B) 370 and a data field (DATA) 372.

The 802.11ac preamble 364 may accommodate backwards compatibility (withearlier 802.11 specifications, for instance). The first part of thepreamble 364 may include the L-STF 356, L-LTF 358, L-SIG 360, VHT-SIG-A1362 a and VHT-SIG-A2 362 b. This first part of the preamble 364 may bedecodable by legacy devices (e.g., devices that comply with legacy orearlier specifications).

A second part of the preamble 364 includes the VHT-STF 366, six VHT-LTFs368 a-f, and the VHT-SIG-B 370. The second part of the preamble 364 maynot be decodable by legacy devices (or even by all 802.11ac devices, forinstance).

The 802.11ac preamble 364 may include some control data that isdecodable by legacy 802.11a and 802.11n receivers. This control data maybe contained in the L-SIG 360. The data in the L-SIG 360 informs allreceivers how long the transmission will occupy the wireless medium, sothat all devices may defer their transmissions for an accurate amount oftime. Additionally, the 802.11ac preamble 364 may allow 802.11ac devicesto distinguish the transmission as an 802.11ac transmission (and avoiddetermining that the transmission is in an 802.11a or 802.11n format,for example).

In accordance with the systems and methods disclosed herein, the sixVHT-LTFs 368 a-f may be mapped using a first matrix (e.g., P matrix) 110with at least one column multiplied by −1. For example, when five or sixstreams 130 are used for transmitting VHT-LTFs 368 a-f, then sixVHT-LTFs 368 a-f may be used in the frame (e.g., packet) 300 asillustrated in FIG. 3. The transmitting communication device 102 mayapply the P matrix 110 to the data or sequences in the VHT-LTFs 368 a-f.More specifically, a transmitting communication device 102 may multiplythe VHT-LTF data (e.g., sequence) in the first VHT-LTF 368 a on a firststream 130 by the first element of the first row of the P matrix 110.Additionally, the transmitting communication device 102 may respectivelymultiply the data or sequences in each of the second through sixthVHT-LTFs 368 b-f on the first stream 130 by the second through sixthelements of the first row of the P matrix 110. Additionally, thetransmitting communication device 102 may respectively multiply the dataor sequences in six VHT-LTFs 368 a-f on a second through fifth or sixthstream 130 by respective rows of the P matrix 110. It should be notedthat in a case where five streams 130 are used, the sixth row of the Pmatrix 110 may not be used. For example, when applying the first matrix(e.g., P matrix) 110 in a five stream 130 case, the sixth row of thefirst matrix (e.g., P matrix) 110 may not be multiplied with any data orsequence. The transmitting communication device 102 may similarly applya second matrix (e.g., R matrix) 112 to pilots (e.g., pilot sequences)included in each VHT-LTF 368 a-f on five or six streams 130.

FIG. 4 is a flow diagram illustrating one configuration of a method 400for generating a matrix-mapped sequence. A transmitting communicationdevice 102 may generate 402 a sequence. For example, the transmittingcommunication device 102 may generate 402 one or more training sequencesfor each VHT-LTF (e.g., VHT-LTF data) to be transmitted in a frame. Atraining sequence (e.g., VHT-LTF data) may comprise a series of values,symbols or tones that may be used to estimate a channel (e.g., amultiple input and multiple output (MIMO) channel).

The transmitting communication device 102 may apply 404 a first matrix(e.g., P matrix) 110 with at least one column multiplied by −1 to thesequence. For instance, the transmitting communication device 102 maymultiply the sequence (e.g., VHT-LTF sequence, VHT-LTF data, trainingsequence, etc.) in each VHT-LTF by a corresponding element of the Pmatrix 110. As described above, the P matrix 110 may be a DFT matrix asillustrated in Equation (3) that has had one or more of its columnsmultiplied by −1. In one configuration, the transmitting communicationdevice 102 may apply 404 the P matrix 110 to the sequence by multiplyingthe sequence in each VHT-LTF by a corresponding element of the P matrix110 illustrated in Equation (1). Alternatively, the P matrix 110illustrated in Equation (2) may be used. In one configuration, thetransmitting communication device 102 may multiply sequences in sixVHT-LTFs on five or six streams 130 by corresponding elements of the Pmatrix 110.

The transmitting communication device 102 may transmit 406 the sequence.For example, the transmitting communication device 102 may transmit 406the sequence that has had the first matrix (e.g., P matrix) 110 appliedto it. For instance, the transmitting communication device 102 maytransmit 406 VHT-LTF data in six VHT-LTFs on five or six streams 130that has been multiplied by the P matrix 110.

FIG. 5 is a flow diagram illustrating a more specific configuration of amethod 500 for generating a matrix-mapped sequence. A transmittingcommunication device 102 may generate 502 a very high throughput longtraining field (VHT-LTF) sequence (e.g., VHT-LTF data). For example, thetransmitting communication device 102 may generate 502 one or moretraining sequences for each VHT-LTF (e.g., VHT-LTF data) to betransmitted in a frame. A training sequence (e.g., VHT-LTF data) maycomprise a series of values, symbols or tones that may be used toestimate a channel (e.g., a multiple input and multiple output (MIMO)channel).

The transmitting communication device 102 may generate 504 a pilotsequence. For example, the transmitting communication device 102 maygenerate 504 a pilot sequence for each VHT-LTF (e.g., VHT-LTF pilots). Apilot sequence may be a group or series of pilot values, symbols ortones that may be used to track phase and/or frequency offsets intransmitted signals.

The transmitting communication device 102 may combine 506 the pilotsequence and the VHT-LTF sequence. For example, the transmittingcommunication device 102 may combine 506 the pilots and VHT-LTF sequenceby inserting the pilots into particular subcarriers 132 of an OFDMsymbol that includes the VHT-LTF sequence.

The transmitting communication device 102 may apply 508 a P matrix 110with at least one column multiplied by −1 to the VHT-LTF sequence. Forinstance, the transmitting communication device 102 may multiply theVHT-LTF sequence (e.g., VHT-LTF data) in each VHT-LTF by a correspondingelement of the P matrix 110. As described above, the P matrix 110 may bea DFT matrix as illustrated in Equation (3) that has had one or more ofits columns multiplied by −1. In one configuration, the transmittingcommunication device 102 may apply 508 the P matrix 110 to the sequenceby multiplying the sequence in each VHT-LTF by a corresponding elementof the P matrix 110 illustrated in Equation (1). Alternatively, the Pmatrix 110 illustrated in Equation (2) may be used. In one example, whenfive or six streams 130 are used for transmitting VHT-LTFs, then sixVHT-LTFs may be used in a frame (e.g., packet). The transmittingcommunication device 102 may multiply the VHT-LTF data (e.g., sequence)in the first VHT-LTF on a first stream 130 by the first element of thefirst row of the P matrix 110. Additionally, the transmittingcommunication device 102 may respectively multiply the data or sequencesin each of the second through sixth VHT-LTFs on the first stream 130 bythe second through sixth elements of the first row of the P matrix 110.Additionally, the transmitting communication device 102 may respectivelymultiply the data or sequences in six VHT-LTFs on a second through fifthor sixth stream 130 by respective rows of the P matrix 110.

The transmitting communication device 102 may apply 510 an R matrix 112to the pilot sequence. In one configuration, the R matrix 112 may bebased on or correspond to a particular P matrix 110. For example, the Rmatrix 112 may comprise a number of replicas of the first row of the Pmatrix 110. The number of replicas may be a number of space-time streams130 (e.g., N_(STS)). Spectral lines on the pilots may be avoided byhaving a P matrix 110 with a first row that includes one or more valuesof −1 (which may be accomplished by multiplying one or more columns by−1). The transmitting communication device 102 may apply 510 the Rmatrix 112 to the pilot sequence by multiplying the pilot tones (inVHT-LTFs) by the R matrix 112. For instance, the transmittingcommunication device 102 may multiply pilot sequences in six VHT-LTFs onfive or six streams 130 by corresponding elements in the R matrix 112.

The transmitting communication device 102 may transmit 512 the VHT-LTFsequence and the pilot sequence. For example, the transmittingcommunication device 102 may transmit 512 the VHT-LTF sequence that hashad the P matrix 110 applied to it and may transmit the VHT-LTF pilotsequence that has had the R matrix 112 applied to it. For instance, thetransmitting communication device 102 may transmit 512 VHT-LTF data andpilots that have been respectively multiplied by the P matrix 110 andthe R matrix 112 in six VHT-LTFs on five or six streams 130.

FIG. 6 is a flow diagram illustrating another configuration of a method600 for using a matrix-mapped sequence. A receiving communication device134 may receive 602 a sequence that is mapped according to a firstmatrix with at least one column multiplied by −1. For example, thereceiving communication device 134 may receive one or more VHT-LTFs fromthe transmitting communication device 102 that include one or moresequences that have been mapped using a first matrix (e.g., P matrix)110 with at least one column multiplied by −1. For instance, thereceiving communication devices may receive 602 six sequences (e.g.,VHT-LTFs) that have been mapped using a first matrix (e.g., P matrix)110 with at least one column multiplied by −1. As described above, thefirst matrix (e.g., P matrix) 110 may be the DFT matrix illustrated inEquation (3) that has had one or more columns multiplied by −1.

The receiving communication device 134 may additionally receive pilotsthat are mapped according to a second matrix (e.g., R matrix) 112. Inone configuration, the R matrix 112 is based on or corresponds to the Pmatrix 110, where the R matrix 112 comprises a number of replicas of thefirst row of the P matrix 110. In one example, the receivingcommunication device 134 may receive pilots that have been mappedaccording to the R matrix 112 in six VHT-LTFs on five or six streams130. The pilots may be used to track (and/or compensate for) frequencyand phase offsets in the received signal.

The receiving communication device 134 may determine 604 a channelestimate based on the sequence. For example, the matrix-mapped sequencein one or more VHT-LTFs may be used to estimate a MEMO channel used totransmit the VHT-LTFs from the transmitting communication device 102 tothe receiving communication device 134.

The receiving communication device 134 may perform 606 an operationbased on the channel estimate. For example, the receiving communicationdevice 134 may use the channel estimate to demodulate and/or decode data(e.g., VHT-DATA) received from the transmitting communication device102. In one configuration, the receiving communication device 134 mayadditionally or alternatively send (e.g., transmit) the channel estimateto the transmitting communication device 102. The transmittingcommunication device 102 may then use the channel estimate forprecoding, beamforming, etc., for example.

FIG. 7 is a block diagram illustrating one configuration of an accesspoint (AP) 702 and a station (STA) 734 in which systems and methods forusing a matrix-mapped sequence may be implemented. The access point 702may include a sequence generation block/module 704, a pilot insertionblock/module 706, a mapping block/module 708, a cyclic shiftblock/module 714, a spatial mapping block/module 716, an InverseDiscrete Fourier Transform (IDFT) block/module 718, a guard intervalblock/module 720, one or more transmit radio frequency blocks 722, oneor more antennas 728 a-n, a pseudo-random noise generator 724, a pilotgenerator 726 and/or a receiver 776.

It should be noted that one or more of the elements 704, 706, 708, 714,716, 718, 720, 722, 724, 726, 776 included in the access point 702 maybe implemented in hardware, software or a combination of both.Furthermore, the term “block/module” may be used to indicate that aparticular element may be implemented in hardware, software or acombination of both. It should also be noted that although some of theelements 704, 706, 708, 714, 716, 718, 720, 722, 724, 726, 776 may beillustrated as a single block, one or more of the elements 704, 706,708, 714, 716, 718, 720, 722, 724, 726, 776 illustrated may comprisemultiple parallel blocks/modules in some configurations. For instance,multiple sequence generation blocks/modules 704, multiple pilotinsertion blocks/modules 706, multiple mapping blocks/modules 708,multiple cyclic shift blocks/modules 714, multiple spatial mappingblocks/modules 716, multiple inverse discrete Fourier transformblocks/modules 718, multiple guard interval blocks/modules 720 and/ormultiple transmit radio frequency block(s) 722 may be used to formmultiple paths in some configurations.

For instance, separate streams 730 (e.g., space-time streams 730,spatial streams 730, etc.) may be generated and/or transmitted usingseparate paths. In some implementations, these paths are implementedwith distinct hardware, whereas in other implementations, the pathhardware is reused for more than one stream 730 or the path logic isimplemented in software that executes for one or more streams 730. Morespecifically, each of the elements illustrated in the access point 702may be implemented as a single block/module or as multipleblocks/modules.

The sequence generation block/module 704 may generate one or moretraining sequences (e.g., “VHT-LTF data” or “VHT-LTF sequences”). Forexample, the sequence generation block/module 704 may generate one ormore training sequences for each VHT-LTF to be transmitted in a frame.In some configurations, the sequence generation block/module 704 maygenerate a sequence in the frequency domain based on an amount oftransmission bandwidth. For example, different sequences may begenerated based on whether 20 megahertz (MHz), 40 MHz, 80 MHz or 160 MHzof bandwidth is allocated for transmission. The sequence(s) may beprovided to the pilot insertion block/module 706.

The pilot generator 726 may generate a pilot sequence. A pilot sequencemay be a group of pilot symbols. In one configuration, for instance, thevalues in the pilot sequence may be represented by a signal with aparticular phase, amplitude and/or frequency. For example, a “1” maydenote a pilot symbol with a particular phase and/or amplitude, while a“−1” may denote a pilot symbol with a different (e.g., opposite orinverse) phase and/or amplitude.

The access point 702 may include a pseudo-random noise generator 724 insome configurations. The pseudo-random noise generator 724 may generatea pseudo-random noise sequence or signal (e.g., values) used to scramblethe pilot sequence. For example, the pilot sequence for successiveorthogonal frequency-division multiplexing (OFDM) symbols may bemultiplied by successive numbers from the pseudo-random noise sequence,thereby scrambling the pilot sequence per OFDM symbol.

The pilot insertion block/module 706 inserts pilot tones into pilot tonesubcarriers 732. For example, the pilot sequence may be mapped tosubcarriers 732 at particular indices. For instance, pilot symbols fromthe (scrambled) pilot sequence may be mapped to pilot subcarriers 732that are interspersed with data subcarriers 732 and/or other subcarriers732. In other words, the pilot sequence or signal may be combined withthe data sequence or signal. In some configurations, one or more directcurrent (DC) tones may be centered at a subcarrier index 0. The pilotinsertion block/module 706 may apply phase rotation to the combinedsignal (e.g., to one or more 20 MHz subbands) in some configurations.

The combined data and pilot signal may be provided to the mappingblock/module 708. The mapping block/module 708 may apply matrix mappingto the data tones (e.g., a training sequence) and/or to the pilot tones(e.g., pilot sequence) included in the combined signal to produce amatrix-mapped signal. The mapping block/module 708 may include a Pmatrix 710 and/or an R matrix 712.

In one example, the P matrix 710 provides a mapping for the data tones(e.g., training sequence) in one or more very high throughput longtraining fields (VHT-LTFs). The P matrix 710 may have at least one ofits 710 columns multiplied by −1. For example, the first matrix 710 maybe a DFT matrix P_(original) that has had one or more of its columnsmultiplied by −1, where P_(original) is given in Equation (3) above. Onespecific example of the P matrix 710 is given above in Equation (1). Theexample given in Equation (1) may be used because the first row ofP_(6×6) in Equation (1) may be equal to the first row of a four-by-fourP matrix {1,−1,1,1}, with the first two values repeated at the end. Itshould be noted that multiplying any column by −1 does not change theorthogonality of the P matrix 710. Another specific example of the Pmatrix 710 is given above in Equation (2).

The data tones (e.g., training sequence, VHT-LTF sequence) in thecombined signal may be multiplied by elements of the P matrix 710. Forexample, each column of the P matrix 710 may correspond to a VHT-LTF andeach row of the P matrix 710 may correspond to a stream 730. Thus, theexample of the P matrix 710 given in Equation (1) may be applied to sixVHT-LTFs on six streams 730 (e.g., spatial streams 730 or space-timestreams 730). More specifically, for instance, data tones in a firstVHT-LTF on a first stream 730 may be multiplied by the element in thefirst column and first row of the P matrix 710. Furthermore, data tonesin a second VHT-LTF on a first stream may be multiplied by the secondelement in the first row of the P matrix 710 and so on. It should benoted that a six-by-six P matrix 710 may be applied when five or sixstreams 730 (e.g., spatial streams 730, space-time streams 730) are usedfor transmitting data tones (e.g., one or more training sequences) insome configurations. Other P matrices may be used for different numbersof streams 730, for instance.

In one configuration, the R matrix 712 provides a mapping for the pilottones in one or more VHT-LTFs. For example, the pilot tones in one ormore VHT-LTFs on one or more streams 730 (e.g., spatial streams 730 orspace-time streams 730) may be multiplied by the R matrix 712.

The R matrix 712 may include a number of replicas of the first row ofthe P matrix 710. In one configuration, the R matrix 712 includesN_(STS) replicas of the first row of the P matrix 710, where N_(STS) isa number of space-time streams 730. As described above, one problemaddressed by the systems and methods disclosed herein is the formationof spectral lines on the pilots. This may occur if the first row of a Pmatrix 710 is all ones in the case of six VHT-LTFs. However, inaccordance with the systems and methods disclosed herein, one or more ofthe columns of the P matrix 710 may be multiplied by −1, thus avoiding afirst row of all ones in the P matrix 710.

The output of the mapping block/module 708 (e.g., a matrix-mappedsignal) may be provided to the cyclic shift block/module 714. The cyclicshift block/module 714 may insert cyclic shifts to one or more streams730 (e.g., spatial streams 730 or space-time streams 730) for cyclicshift diversity (CSD). In one configuration, cyclic shifts may beapplied to multiple transmit chains.

The output of the cyclic shift block/module 714 may be provided to aspatial mapping block/module 716. The spatial mapping block/module 716may map output of the cyclic shift block/module 714 (e.g., data tonesand/or pilot tones) to one or more streams 730 (e.g., spatial streams730 or space-time streams 730).

The IDFT block/module 718 may perform an inverse discrete Fouriertransform on the signal provided by the spatial mapping block/module716. For example, the inverse discrete Fourier transform (IDFT)block/module 718 converts the frequency signals of the data tones and/orpilot tones into time domain signals representing the signal over thestreams 730 and/or time-domain samples for a symbol period. In oneconfiguration, for example, the IDFT block/module 718 may perform aninverse fast Fourier transform (IFFT).

The signal output from the IDFT block/module 718 may be provided to theguard interval block/module 720. The guard interval block/module 720 mayinsert (e.g., prepend) a guard interval to the signal output from theIDFT block/module 718. For example, the guard interval block/module 720may insert an 800 nanosecond (ns) guard interval. In someconfigurations, the guard interval block/module 720 may additionallyperform windowing on the signal.

The output of the guard interval block/module 720 may be provided to thetransmit radio frequency block(s) 722. The transmit radio frequencyblock(s) 722 may upconvert the output of the guard interval block/module720 (e.g., a complex baseband waveform) and transmit the resultingsignal using the one or more antennas 728 a-n. For example, the one ormore transmit radio frequency block(s) 722 may output radio-frequency(RF) signals to one or more antennas 728 a-n, thereby transmitting thedata tones (e.g., VHT-LTF sequence) and/or pilot tones (e.g., VHT-LTFpilots) over a wireless medium suitably configured for receipt by one ormore stations 734.

It should be noted that the access point 702 may determine channelbandwidth to be used for transmissions to one or more stations 734. Thisdetermination may be based on one or more factors, such as station 734compatibility, number of stations 734 (to use the communicationchannel), channel quality (e.g., channel noise) and/or a receivedindicator, etc. In one configuration, the access point 702 may determinewhether the bandwidth for signal transmission is 20 MHz, 40 MHz, 80 MHzor 160 MHz.

One or more of the elements 704, 706, 708, 714, 716, 718, 720, 722, 724,726, 776 included in the access point 702 may operate based on thebandwidth determination. For example, the sequence generationblock/module 704 may generate one or more particular training sequences(e.g., VHT-LTF data tones) based on transmission bandwidth. Additionallyor alternatively, the pilot generator 726 may generate a number of pilotsymbols based on the bandwidth for signal transmission. For example, thepilot generator 726 may generate a certain number of pilot symbols foran 80 MHz signal. It should be noted that the tones or subcarriers 732may be orthogonal frequency-division multiplexing (OFDM) subcarriers 732in some configurations.

Additionally, the pilot insertion block/module 706 may insert pilottones based on a bandwidth for signal transmission. For instance, thepilot insertion block/module 706 may insert pilot symbols into pilottones (e.g., pilot subcarriers 732) based on a bandwidth for signaltransmission.

Additionally, the mapping block/module 708 may matrix map the data tonesand/or pilot tones based on the bandwidth for signal transmission. Forinstance, the mapping block/module 708 may matrix map a number of datatones (e.g., data subcarriers 732) and a number of pilot tones (e.g.,pilot subcarriers 732) based on a bandwidth for signal transmission.

One or more streams 730 may be transmitted from the access point 702such that the transmissions on different streams 730 may bedifferentiable at a station 734 (with some probability). For example,bits mapped to one spatial dimension are transmitted as one stream 730.That stream 730 might be transmitted on its own antenna 728 spatiallyseparate from other antennas 728, its own orthogonal superposition overa plurality of spatially-separated antennas 728, its own polarization,etc. Many techniques for stream 730 separation (involving separatingantennas 728 in space or other techniques that would allow their signalsto be distinguished at a receiver, for example) are known and can beused. In the example shown in FIG. 7, there are one or more streams 730that are transmitted using the same or a different number of antennas728 a-n (e.g., one or more).

In the case that the access point 702 uses a plurality of frequencysubcarriers 732, there are multiple values for the frequency dimension,such that some data (e.g., some VHT-LTF data) may be mapped to onefrequency subcarrier 732 and other data (e.g., other VHT-LTF data) toanother frequency subcarrier 732. Other frequency subcarriers 732 may bereserved as guard bands, pilot tone subcarriers 732, or the like that donot (or do not always) carry data. For example, there may be one or moredata subcarriers 732 and one or more pilot subcarriers 732. It should benoted that, in some instances or configurations, not all subcarriers 732may be excited at once. For instance, some tones may not be excited toenable filtering. In one configuration, the access point 702 may utilizeorthogonal frequency-division multiplexing (OFDM) for the transmissionof multiple subcarriers 732.

The time dimension refers to symbol periods. Different bits may beallocated to different symbol periods. Where there are multiple streams730, multiple subcarriers 732 and multiple symbol periods, thetransmission for one symbol period might be referred to as an “OFDM(orthogonal frequency-division multiplexing) MIMO (multiple-input,multiple-output) symbol.” A transmission rate for encoded data may bedetermined by multiplying the number of bits per simple symbol (e.g.,log₂ of the number of constellations used) times the number of streams730 times the number of data subcarriers 732, divided by the length ofthe symbol period.

One or more stations 734 may receive and use signals from the accesspoint 702. For example, a station 734 may use a received bandwidthindicator to receive a given number of OFDM tones or subcarriers 732. Inone configuration, a station 734 may use a VHT-LTF sequence generated byand received from the access point 702 to estimate the channel. Itshould be noted that one or more of the elements included in the station(STA) 734 may be implemented in software, hardware or a combination ofboth.

A station 734 may include one or more antennas 754 a-n (which may begreater than, less than or equal to the number of access point 702antennas 728 a-n and/or the number of streams 730) that feed to one ormore receive radio frequency blocks 752. The receive radio frequencyblock(s) 752 may output analog signals to one or more analog-to-digitalconverters (ADCs) 750. For example, a receive radio frequency block 752may receive and downconvert a signal, which may be provided to ananalog-to-digital converter 750. As with the access point 702, thenumber of streams 730 processed may or may not be equal to the number ofantennas 754 a-n. Furthermore, each stream 730 need not be limited toone antenna 754, as various beamsteering, orthogonalization, etc.techniques may be used to arrive at a plurality of receiver streams.

The one or more analog-to-digital converters (ADCs) 750 may convert thereceived analog signal(s) to one or more digital signal(s). Theoutput(s) of the one or more analog-to-digital converters (ADCs) 750 maybe provided to one or more time and/or frequency synchronizationblocks/modules 748. A time and/or frequency synchronization block/module748 may (attempt to) synchronize or align the digital signal in timeand/or frequency (to a station 734 clock, for example).

The (synchronized) output of the time and/or frequency synchronizationblock(s)/module(s) 748 may be provided to one or more deformatters 746.For example, a deformatter 746 may receive an output of the time and/orfrequency synchronization block(s)/module(s) 748, remove guardintervals, etc. and/or parallelize the data for discrete Fouriertransform (DFT) processing.

One or more deformatter 746 outputs may be provided to one or morediscrete Fourier transform (DFT) blocks/modules 744. The discreteFourier transform (DFT) blocks/modules 744 may convert one or moresignals from the time domain to the frequency domain. A pilot processor742 may use the frequency domain signals (per stream 730, for example)to determine one or more pilot tones (over the streams 730, frequencysubcarriers 732 and/or groups of symbol periods, for example) sent bythe access point 702. The pilot processor 742 may additionally oralternatively de-scramble the pilot sequence. The pilot processor 742may use one or more pilot sequences described herein for phase,frequency and/or amplitude tracking. The pilot tone(s) may be providedto a space-time-frequency detection and/or decoding block/module 740,which may detect and/or decode the data over the various dimensions. Thespace-time-frequency detection and/or decoding block/module 740 mayoutput received data 736 (e.g., the station's 734 estimation of datatransmitted by the access point 702).

In some configurations, the station 734 knows the sequences (e.g.,VHT-LTF data, training sequences, etc.) sent as part of a totalinformation sequence. The station 734 may perform channel estimationwith the aid of these known sequences. To assist with pilot tonetracking, processing and/or data detection and decoding, a channelestimation block/module 738 may provide estimation signals (e.g.,channel estimates) to the pilot processor 742, to thespace-time-frequency detection and/or decoding block/module 740 and/orto the transmitter 780 (e.g., transmitter circuitry) based on the outputfrom the time and/or frequency synchronization block/module 748.Alternatively, if the de-formatting and discrete Fourier transform isthe same for the known transmit sequences as for the payload dataportion of the total information sequence, the estimation signals may beprovided to the pilot processor 742, to the space-time-frequencydetection and/or decoding block/module 740 and/or to the transmitter 780based on the output from the discrete Fourier transform (DFT)blocks/modules 744.

In accordance with the systems and methods disclosed herein, the station734 may receive a sequence (e.g., VHT-LTF data) that is mapped accordingto a matrix with a least one column multiplied by −1. For example, thestation 734 may receive a VHT-LTF sequence or VHT-LTF data (e.g.,training sequence) that has been mapped using the P matrix 710 that hasat least one of its columns multiplied by −1. For instance, the DFTmatrix illustrated in Equation (3) with one or more of its columnsmultiplied by −1 may be used to map the VHT-LTF data or sequence that isreceived by the station 734.

The station 734 (e.g., channel estimation block/module 738) may use thereceived data or sequence to generate a channel estimate. The station734 may use the channel estimate to improve communications between theaccess point 702 and the station 734. For example, the station 734 mayuse the channel estimate to better receive (e.g., demodulate, decode,etc.) data sent from the access point 702. Additionally oralternatively, the station 734 may send the channel estimate (asfeedback) to the access point 702 for use in precoding, beamsteering,etc. In some configurations, for instance, the station 734 may include atransmitter 780 for transmitting the channel estimate to the accesspoint 702. Accordingly, the access point 702 may also include a receiver776 for receiving signals (such as the channel estimate) from thestation 734 in some configurations. Received pilot tones in the VHT-LTFmay be used to track frequency and phase offset in receivedtransmissions.

In some configurations, the station 734 may determine a channelbandwidth (for received communications). For example, the station 734may receive a bandwidth indication from the access point 702 thatindicates a channel bandwidth. For instance, the station 734 may obtainan explicit or implicit bandwidth indication. In one configuration, thebandwidth indication may indicate a channel bandwidth of 20 MHz, 40 MHz,80 MHz or 160 MHz. The station 734 may determine the bandwidth forreceived communications based on this indication and provide anindication of the determined bandwidth to the pilot processor 742 and/orto the space-time-frequency detection/decoding block/module 740.

In the configuration illustrated in FIG. 7, the station 734 may includea transmitter 780. The transmitter 780 may perform similar operations asthose performed by one or more of the elements 706, 708, 714, 716, 718,720, 722, 724, 726 included in the access point 702 in order to transmita sequence (that has been mapped using a matrix with at least one columnmultiplied by −1) provided by a sequence generation block/module 778.

In the configuration illustrated in FIG. 7, the access point 702 mayinclude a receiver 776. The receiver 776 may perform similar operationsas those performed by one or more of the elements 740, 742, 744, 746,748, 750, 752, 738 included in the station 734 in order to receive asequence (that has been mapped using a matrix with at least one columnmultiplied by −1) from one or more stations 734. For example, thereceiver 776 may perform one or more functions in order to providereceived data 774 and/or to provide a channel estimate to the transmitradio frequency block(s) 722. Thus, as illustrated in FIG. 7,bi-directional communications between the access point 702 and thestation 734 may occur on one or more streams 730 and on one or moresubcarriers 732. In one configuration, this may allow bi-directionalchannel estimate feedback between the access point 702 and the station734.

FIG. 8 is a block diagram of a communication device 882 that may be usedin a multiple-input and multiple-output (MIMO) system. Examples of thecommunication device 882 may include transmitting communication devices102, receiving communication devices 134, access points (APs) 702,stations (STAs) 734, base stations, user equipments (UEs), etc. In thecommunication device 882, data for a number of data streams is providedfrom one or more data sources 884 and/or an application processor 886 toa baseband processor 890. In particular, data may be provided to atransmit processing block/module 894 included in the baseband processor890. Each data stream may then be transmitted over a respective transmitantenna 811 a-n. The transmit processing block/module 894 may format,code and/or interleave the data for each data stream based on aparticular coding scheme selected for that data stream to provide codeddata.

The transmit processing block/module 894 may perform one or more of themethods 400, 500 illustrated in FIGS. 4 and 5. For example, the transmitprocessing block/module 894 may include a mapping block/module 896. Themapping block/module 896 may execute instructions in order to map data(e.g., a VHT-LTF sequence) and/or pilots (e.g., VHT-LTF pilots) asdescribed above.

The coded data for each data stream may be multiplexed with pilot datafrom a pilot generator 892 using orthogonal frequency-divisionmultiplexing (OFDM) techniques. The pilot data may be a known datapattern that is processed in a known manner and used at a receiver totrack phase and/or frequency offsets. The multiplexed pilot and codeddata for each stream may then be modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., binary phase shift keying(BPSK), quadrature phase shift keying (QPSK), multiple phase shiftkeying (M-PSK), quadrature amplitude modulation (QAM) or multi-levelquadrature amplitude modulation (M-QAM)) selected for that data streamto provide modulation symbols. The data rate, coding and modulation foreach data stream may be determined by instructions performed by aprocessor (e.g., baseband processor 890, application processor 886,etc.).

The modulation symbols for all data streams may be provided to atransmit (TX) multiple-input multiple-output (MIMO) processingblock/module 805, which may further process the modulation symbols (forOFDM, for example). The transmit (TX) multiple-input multiple-output(MIMO) processing block/module 805 then provides a number of modulationsymbol streams to the transmitters 809 a-n. The transmit (TX)multiple-input multiple-output (MIMO) processing block/module 805 mayapply beamforming weights to the symbols of the data streams and to theantenna 811 from which the symbol is being transmitted.

Each transmitter 809 a-n may receive and process a respective symbolstream to provide one or more analog signals, and further condition(e.g., amplify, filter, and upconvert) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel.Modulated signals from the transmitters 809 a-n are then respectivelytransmitted from the antennas 811 a-n. For example, the modulated signalmay be transmitted to another communication device (not illustrated inFIG. 8).

The communication device 882 may receive modulated signals (from anothercommunication device). These modulated signals are received by antennas811 and conditioned by receivers 809 (e.g., filtered, amplified,downconverted, digitized). In other words, each receiver 809 a-n maycondition (e.g., filter, amplify, and downconvert) a respective receivedsignal, digitize the conditioned signal to provide samples, and furtherprocess the samples to provide a corresponding “received” symbol stream.

A receive processing block/module 801 included in the baseband processor890 then receives and processes the received symbol streams from thereceivers 809 based on a particular receiver processing technique toprovide a number of “detected” streams. The receive processingblock/module 801 may demodulate, deinterleave and decode each stream torecover the data for the data stream.

The receive processing block/module 801 may perform the method 600illustrated in FIG. 6 in some configurations. For example, the receiveprocessing block/module 801 may include a channel estimationblock/module 803. The channel estimation block/module 803 may executeinstructions to estimate a channel based on a received sequence that hasbeen mapped using a matrix with at least one column multiplied by −1.Additionally or alternatively, the receive processing block/module 801may receive a channel estimate from another device.

A precoding processing block/module 898 included in the basebandprocessor 890 may receive channel state information (CSI), which mayinclude a channel estimate, from the receive processing block/module801. The precoding processing block/module 898 then determines whichpre-coding matrix to use for determining the beamforming weights andthen processes the extracted message. It should be noted that thebaseband processor 890 may store information on and retrieve informationfrom baseband memory 807.

Data recovered by the baseband processor 890 may be provided to theapplication processor 886. The application processor 886 may storeinformation in and retrieve information from the application memory 888.

It should be noted that the communication device 882 may include themapping block/module 896 or the channel estimation block/module 803, butnot both, in some configurations. In other configurations, thecommunication device 882 may include both the mapping block/module 896and the channel estimation block/module 803.

In one configuration, the communication device 882 may include themapping block/module 896, but not the channel estimation block/module803. In this configuration, the mapping block/module 896 may map asequence (e.g., VHT-LTF data or VHT-LTF sequence) using a first matrix(e.g., P matrix) with at least one column multiplied by −1. The sequence(e.g., a VHT-LTF) may then be transmitted to another device. The otherdevice may use the sequence to generate a channel estimate, which may betransmitted back to the communication device 882. The communicationdevice 882 (e.g., receive processing block/module 801) may extract thechannel estimate (as channel state information (CSI), for example),which may be provided to the precoding processing block/module 898 forprecoding signals for transmission.

In another configuration, the communication device 882 may include thechannel estimation block/module 803, but not the mapping block/module896. In this configuration, the communication device 882 may optionallysend a training request to another device. The communication device 882may receive a sequence (e.g., VHT-LTF sequence) that has been mappedusing a matrix (e.g., P matrix) with at least one column multiplied by−1. The channel estimation block/module 803 may use the sequence togenerate a channel estimate (e.g., channel state information (CSI)). Thechannel estimate may be transmitted to the other device, which may usethe channel estimate for precoding signals for transmission (whichsignals may be received by the communication device 882).

In yet another configuration, the communication device 882 may includeboth the mapping block/module 896 and the channel estimationblock/module 803. In this configuration, the communication device 882may send a matrix-mapped sequence to another device, which may be usedto generate a channel estimate that is fed back to the communicationdevice 882 for improving transmissions (e.g., precoding). Thecommunication device may additionally receive a separate matrix-mappedsequence from another device and use this sequence to generate aseparate channel estimate that is fed back to the other device for usein improving transmissions (e.g., precoding).

FIG. 9 illustrates certain components that may be included within acommunication device 913. The transmitting communication device 102,receiving communication device 134, access point 702, station (STA) 734and/or communication device 882 described above may be configuredsimilarly to the communication device 913 that is shown in FIG. 9.

The communication device 913 includes a processor 931. The processor 931may be a general purpose single- or multi-chip microprocessor (e.g., anARM), a special purpose microprocessor (e.g., a digital signal processor(DSP)), a microcontroller, a programmable gate array, etc. The processor931 may be referred to as a central processing unit (CPU). Although justa single processor 931 is shown in the communication device 913 of FIG.9, in an alternative configuration, a combination of processors (e.g.,an advanced reduced instruction set computer (RISC) machine (ARM) anddigital signal processor (DSP)) could be used.

The communication device 913 also includes memory 915 in electroniccommunication with the processor 931 (i.e., the processor 931 can readinformation from and/or write information to the memory 915). The memory915 may be any electronic component capable of storing electronicinformation. The memory 915 may be random access memory (RAM), read-onlymemory (ROM), magnetic disk storage media, optical storage media, flashmemory devices in RAM, on-board memory included with the processor,programmable read-only memory (PROM), erasable programmable read-onlymemory (EPROM), electrically erasable PROM (EEPROM), registers, and soforth, including combinations thereof.

Data 917 a and instructions 919 a may be stored in the memory 915. Theinstructions 919 a may include one or more programs, routines,sub-routines, functions, procedures, code, etc. The instructions 919 amay include a single computer-readable (e.g., processor-readable)statement or many computer-readable statements. The instructions 919 amay be executable by the processor 931 to implement one or more of themethods 400, 500, 600 described above. Executing the instructions 919 amay involve the use of the data 917 a that is stored in the memory 915.FIG. 9 shows some instructions 919 b and data 917 b being loaded intothe processor 931 (which may come from instructions 919 a and data 917 ain memory 915).

The communication device 913 may also include a transmitter 927 and areceiver 929 to allow transmission and reception of signals between thecommunication device 913 and a remote location (e.g., anothercommunication device, access terminal, access point, etc.). Thetransmitter 927 and receiver 929 may be collectively referred to as atransceiver 925. An antenna 923 may be electrically coupled to thetransceiver 925. The communication device 913 may also include (notshown) multiple transmitters, multiple receivers, multiple transceiversand/or multiple antenna.

The various components of the communication device 913 may be coupledtogether by one or more buses, which may include a power bus, a controlsignal bus, a status signal bus, a data bus, etc. For simplicity, thevarious buses are illustrated in FIG. 9 as a bus system 921.

FIG. 10 illustrates certain components that may be included within awireless communication device 1033. One or more of the transmittingcommunication device 102, receiving communication device 134, station(STA) 734 and communication device 882 described above may be configuredsimilarly to the wireless communication device 1033 that is shown inFIG. 10.

The wireless communication device 1033 includes a processor 1053. Theprocessor 1053 may be a general purpose single- or multi-chipmicroprocessor (e.g., an ARM), a special purpose microprocessor (e.g., adigital signal processor (DSP)), a microcontroller, a programmable gatearray, etc. The processor 1053 may be referred to as a centralprocessing unit (CPU). Although just a single processor 1053 is shown inthe wireless communication device 1033 of FIG. 10, in an alternativeconfiguration, a combination of processors 1053 (e.g., an advancedreduced instruction set computer (RISC) machine (ARM) and digital signalprocessor (DSP)) could be used.

The wireless communication device 1033 also includes memory 1035 inelectronic communication with the processor 1053 (i.e., the processor1053 can read information from and/or write information to the memory1035). The memory 1035 may be any electronic component capable ofstoring electronic information. The memory 1035 may be random accessmemory (RAM), read-only memory (ROM), magnetic disk storage media,optical storage media, flash memory devices in RAM, on-board memoryincluded with the processor 1053, programmable read-only memory (PROM),erasable programmable read-only memory (EPROM), electrically erasablePROM (EEPROM), registers, and so forth, including combinations thereof.

Data 1037 a and instructions 1039 a may be stored in the memory 1035.The instructions 1039 a may include one or more programs, routines,sub-routines, functions, procedures, code, etc. The instructions 1039 amay include a single computer-readable (e.g., processor-readable)statement or many computer-readable statements. The instructions 1039 amay be executable by the processor 1053 to implement one or more of themethods 400, 500, 600 described above. Executing the instructions 1039 amay involve the use of the data 1037 a that is stored in the memory1035. FIG. 10 shows some instructions 1039 b and data 1037 b beingloaded into the processor 1053 (which may come from instructions 1039 aand data 1037 a in memory 1035).

The wireless communication device 1033 may also include a transmitter1049 and a receiver 1051 to allow transmission and reception of signalsbetween the wireless communication device 1033 and a remote location(e.g., another electronic device, communication device, etc.). Thetransmitter 1049 and receiver 1051 may be collectively referred to as atransceiver 1047. An antenna 1055 may be electrically coupled to thetransceiver 1047. The wireless communication device 1033 may alsoinclude (not shown) multiple transmitters 1049, multiple receivers 1051,multiple transceivers 1047 and/or multiple antenna 1055.

In some configurations, the wireless communication device 1033 mayinclude one or more microphones 1041 for capturing acoustic signals. Inone configuration, a microphone 1041 may be a transducer that convertsacoustic signals (e.g., voice, speech) into electrical or electronicsignals. Additionally or alternatively, the wireless communicationdevice 1033 may include one or more speakers 1043. In one configuration,a speaker 1043 may be a transducer that converts electrical orelectronic signals into acoustic signals.

The various components of the wireless communication device 1033 may becoupled together by one or more buses, which may include a power bus, acontrol signal bus, a status signal bus, a data bus, etc. Forsimplicity, the various buses are illustrated in FIG. 10 as a bus system1045.

In the above description, reference numbers have sometimes been used inconnection with various terms. Where a term is used in connection with areference number, this may be meant to refer to a specific element thatis shown in one or more of the Figures. Where a term is used without areference number, this may be meant to refer generally to the termwithout limitation to any particular Figure.

The term “determining” encompasses a wide variety of actions and,therefore, “determining” can include calculating, computing, processing,deriving, investigating, looking up (e.g., looking up in a table, adatabase or another data structure), ascertaining and the like. Also,“determining” can include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” can include resolving, selecting, choosing, establishingand the like.

The phrase “based on” does not mean “based only on,” unless expresslyspecified otherwise. In other words, the phrase “based on” describesboth “based only on” and “based at least on.”

The functions described herein may be stored as one or more instructionson a processor-readable or computer-readable medium. The term“computer-readable medium” refers to any available medium that can beaccessed by a computer or processor. By way of example, and notlimitation, such a medium may comprise RAM, ROM, EEPROM, flash memory,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to storedesired program code in the form of instructions or data structures andthat can be accessed by a computer or processor. Disk and disc, as usedherein, includes compact disc (CD), laser disc, optical disc, digitalversatile disc (DVD), floppy disk and Blu-ray® disc where disks usuallyreproduce data magnetically, while discs reproduce data optically withlasers. It should be noted that a computer-readable medium may betangible and non-transitory. The term “computer-program product” refersto a computing device or processor in combination with code orinstructions (e.g., a “program”) that may be executed, processed orcomputed by the computing device or processor. As used herein, the term“code” may refer to software, instructions, code or data that is/areexecutable by a computing device or processor.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL) or wireless technologiessuch as infrared, radio and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL or wireless technologies such asinfrared, radio and microwave are included in the definition oftransmission medium.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isrequired for proper operation of the method that is being described, theorder and/or use of specific steps and/or actions may be modifiedwithout departing from the scope of the claims.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the systems, methods, and apparatus described herein withoutdeparting from the scope of the claims.

What is claimed is:
 1. (canceled)
 2. A communication device forgenerating a matrix-mapped sequence, comprising: mapping circuitryconfigured to apply a matrix to a sequence, wherein each element in atleast one column of the matrix has a negative value; and a transmitblock coupled to the mapping circuitry and configured to transmit thesequence.
 3. The communication device of claim 2, wherein the matrix isgiven according to an equation ${P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & {- w^{4}} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & {- w^{8}} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & {- w^{12}} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & {- w^{16}} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & {- w^{20}} & {- w^{25}}\end{bmatrix}},$ wherein P_(6×6) is the matrix and$w = {{\exp \left( \frac{- {j2\pi}}{6} \right)}.}$
 4. The communicationdevice of claim 2, wherein at least one column of the at least onecolumn has a first column adjacent to a first side of the at least onecolumn of the at least one column and a second column adjacent to asecond side of the at least one column of the at least one column. 5.The communication device of claim 2, wherein a sum of all elements in atleast one row of the matrix is zero.
 6. A method for generating amatrix-mapped sequence, comprising: applying a matrix to a sequence,wherein each element in at least one column of the matrix has a negativevalue; and transmitting the sequence.
 7. The method of claim 6, whereinthe matrix is given according to an equation${P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & {- w^{4}} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & {- w^{8}} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & {- w^{12}} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & {- w^{16}} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & {- w^{20}} & {- w^{25}}\end{bmatrix}},$ wherein P_(6×6) is the matrix and$w = {{\exp \left( \frac{- {j2\pi}}{6} \right)}.}$
 8. The method ofclaim 6, wherein at least one column of the at least one column has afirst column adjacent to a first side of the at least one column of theat least one column and a second column adjacent to a second side of theat least one column of the at least one column.
 9. The method of claim6, wherein a sum of all elements in at least one row of the matrix iszero.
 10. A non-transitory computer-readable medium for generating amatrix-mapped sequence, the medium comprising processor-readableinstructions configured to cause one or more processors to: apply amatrix to a sequence, wherein each element in at least one column of thematrix has a negative value; and transmit the sequence.
 11. Thenon-transitory computer-readable medium of claim 10, wherein the matrixis given according to an equation ${P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & {- w^{4}} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & {- w^{8}} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & {- w^{12}} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & {- w^{16}} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & {- w^{20}} & {- w^{25}}\end{bmatrix}},$ wherein P_(6×6) is the matrix and$w = {{\exp \left( \frac{- {j2\pi}}{6} \right)}.}$
 12. Thenon-transitory computer-readable medium of claim 10, wherein at leastone column of the at least one column has a first column adjacent to afirst side of the at least one column of the at least one column and asecond column adjacent to a second side of the at least one column ofthe at least one column.
 13. The non-transitory computer-readable mediumof claim 10, wherein a sum of all elements in at least one row of thematrix is zero.
 14. An apparatus for generating a matrix-mappedsequence, comprising: means for applying a matrix to a sequence, whereineach element in at least one column of the matrix has a negative value;and means for transmitting the sequence.
 15. A communication device forusing a matrix-mapped sequence, comprising: a receive block configuredto receive a sequence that is mapped according to a matrix, wherein eachelement in at least one column of the matrix has a negative value; andchannel estimation circuitry coupled to the receive block and configuredto receive a first signal that corresponds to the sequence, to estimatea channel from the first signal, and to produce a second signal thatincludes information about an estimate of the channel.
 16. Thecommunication device of claim 15, wherein the matrix is given accordingto an equation ${P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & {- w^{4}} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & {- w^{8}} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & {- w^{12}} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & {- w^{16}} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & {- w^{20}} & {- w^{25}}\end{bmatrix}},$ wherein P_(6×6) is the matrix and$w = {{\exp \left( \frac{- {j2\pi}}{6} \right)}.}$
 17. Thecommunication device of claim 15, wherein at least one column of the atleast one column has a first column adjacent to a first side of the atleast one column of the at least one column and a second column adjacentto a second side of the at least one column of the at least one column.18. The communication device of claim 15, wherein a sum of all elementsin at least one row of the matrix is zero.
 19. A method for using amatrix-mapped sequence, comprising: receiving a sequence that is mappedaccording to a matrix, wherein each element in at least one column ofthe matrix has a negative value; receiving a first signal thatcorresponds to the sequence; estimating a channel from the first signal;and producing a second signal that includes information about anestimate of the channel.
 20. The method of claim 19, wherein the matrixis given according to an equation ${P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & {- w^{4}} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & {- w^{8}} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & {- w^{12}} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & {- w^{16}} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & {- w^{20}} & {- w^{25}}\end{bmatrix}},$ wherein P_(6×6) is the matrix and$w = {{\exp \left( \frac{- {j2\pi}}{6} \right)}.}$
 21. The method ofclaim 19, wherein at least one column of the at least one column has afirst column adjacent to a first side of the at least one column of theat least one column and a second column adjacent to a second side of theat least one column of the at least one column.
 22. The method of claim19, wherein a sum of all elements in at least one row of the matrix iszero.
 23. A non-transitory computer-readable medium for using amatrix-mapped sequence, the medium comprising processor-readableinstructions configured to cause one or more processors to: receive asequence that is mapped according to a matrix, wherein each element inat least one column of the matrix has a negative value; receive a firstsignal that corresponds to the sequence; estimating a channel from thefirst signal; and produce a second signal that includes informationabout an estimate of the channel.
 24. The non-transitorycomputer-readable medium of claim 23, wherein the matrix is givenaccording to an equation ${P_{6 \times 6} = \begin{bmatrix}1 & {- 1} & 1 & 1 & {- 1} & {- 1} \\1 & {- w^{1}} & w^{2} & w^{3} & {- w^{4}} & {- w^{5}} \\1 & {- w^{2}} & w^{4} & w^{6} & {- w^{8}} & {- w^{10}} \\1 & {- w^{3}} & w^{6} & w^{9} & {- w^{12}} & {- w^{15}} \\1 & {- w^{4}} & w^{8} & w^{12} & {- w^{16}} & {- w^{20}} \\1 & {- w^{5}} & w^{10} & w^{15} & {- w^{20}} & {- w^{25}}\end{bmatrix}},$ wherein P_(6×6) is the matrix and$w = {{\exp \left( \frac{- {j2\pi}}{6} \right)}.}$
 25. Thenon-transitory computer-readable medium of claim 23, wherein at leastone column of the at least one column has a first column adjacent to afirst side of the at least one column of the at least one column and asecond column adjacent to a second side of the at least one column ofthe at least one column.
 26. The non-transitory computer-readable mediumof claim 23, wherein a sum of all elements in at least one row of thematrix is zero.
 27. An apparatus for using a matrix-mapped sequence,comprising: means for receiving a sequence that is mapped according to amatrix, wherein each element in at least one column of the matrix has anegative value; means for receiving a first signal that corresponds tothe sequence; means for estimating a channel from the first signal; andmeans for producing a second signal that includes information about anestimate of the channel.